High Performance Concrete 1992

Addis, B. J. and Alexander, M. G., "A METHOD OF PROPORTIONING TRIAL MIXES FOR HIGH-STRENGTH CONCRETE," Concrete/Beton, 1992, No. 63, pp 16-22.

The paper discusses the need and requirements for a method of proportioning high-strength concrete mixes. The development of the method, which is based on a well established method used for conventional concrete, is described. Design charts are given for various stone sizes and the use of a chart is illustrated by means of a worked example. Because the method is based on easily determined aggregate properties it is suitable for any type of aggregate: crushed or naturally occurring stone and sand, and graded or single-sized stone.

3346
Ahmad, S. H., Zia, P., Leming, M. L., and Hansen, M. R., "MECHANICAL PROPERTIES OF HIGH PERFORMANCE CONCRETES," Proceedings of the 9th Conference on Engineering Mechanics, May 24-27, 1992, College Station, TX,; Ed. by Loren D. Lutes and John M. Niedzwecki; ASCE, New York, 1992, pp 864-867.

This paper presents some of the initial results of a 4-year research project on mechanical properties of high performance concretes with particular reference to highway applications. High performance concrete is defined by certain requirements of strength and durability.

3346a
Alexander, M. G. and Addis, B. J., "PROPERTIES OF HIGH STRENGTH CONCRETE INFLUENCED BY AGGREGATES AND INTERFACIAL BOND," in Bond in Concrete: From Research to Practice, Proceedngs of the CEB International Conference held at Riga Technical University, Oct. 15-17, 1992, Riga, Latvia, Vol. 2, Topics 3-7, pp. 4-19 to 4-26.

Properties of high strength concrete using South African materials are reported. It is shown that aggregates, inter alia, play an important role in governing mechanical properties of HSC. Generally, andesite and dolomite aggregates give superior results. Tests were also done on "artificial" interfaces between paste and these two rock types, in order to characterize the interfacial bond properties. Results show that andesite achieves higher interfacial fracture energy values than dolomite, which helps to confirm the macroscopic engineering properties measured on concretes.

3347
Alfes, C., "MODULUS OF ELASTICITY AND DRYING SHRINKAGE OF HIGH-STRENGTH CONCRETE CONTAINING SILICA FUME," Proceedings of the 4th International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, held May 3-8, 1992, Istanbul, Turkey; Sponsored by CANMET in association with the American Concrete Institute and others; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1992, Vol. 2, pp 1651-71. (ACI SP-132)

Investigations were carried out to determine the influence of the modulus of elasticity of the aggregate on the deformation behavior of high strength concrete. The results show that there is a direct and linear relationship between the shrinkage value and the modulus of elasticity of the concrete. The highest modulus of elasticity of the concrete was 85 GPa. The compressive strength at the age of 28 days was in the range from 102 to 182 MPa. A design aid is presented to show the interrelation between modulus of elasticity and shrinkage strain of the concrete on one side and modulus of elasticity of the aggregate, modulus of elasticity of the matrix and matrix content on the other side.

3348
"ALKALI-SILICA REACTION IN CONCRETE (1990-1992)," Current Topics in Transport, 1992, No. CT 13, 30 pp.

This international bibliography includes abstracts of English language reports, conference papers, books and journal articles on alkali-silica reaction in concrete (ASR). Among the subjects covered are: the causes, detection, measurement, structural implications (especially for bridges), and prevention of ASR in concrete. The items have been selected from the material added to the TRL Library Database between 1990 and 1992.

3349
Al-Nahlawi, K. A. and Wight, J. K., "BEAM ANALYSIS USING CONCRETE TENSILE STRENGTH IN TRUSS MODELS," ACI Structural Journal, May-Jun 1992, Vol. 89, No. 3, pp 284-289.

An analytical approach is applied in this paper to explain shear behavior in reinforced concrete beams with and without shear reinforcement. The analytical approach is based on the force flow in beams. For reinforced concrete beams with web reinforcement, compression forces are resisted by concrete and tension forces are resisted by reinforcing steel. For reinforced concrete beams without web reinforcement, concrete tension elements are used to resist the tension forces in the beam. The compression struts are inclined at an angle of approximately 35 degrees. Truss models based on this criteria are able to predict the failure loads of reinforced concrete beams reasonably well. In this study, beams with concrete strengths ranging from 5,000 psi to in excess of 10,000 psi are analyzed. The test results agree well with the analytical results.

3350
Armaghani, J. M., Larsen, T. J., and Romano, D. C., "ASPECTS OF CONCRETE STRENGTH AND DURABILITY," Transportation Research Record, 1992, No. 1335, pp 63-69.

This paper presents the results of the first phase of the research on the strength and durability of concrete in Florida. Twenty-two concrete mixtures were prepared and tested for compressive strength, water permeability, chloride permeability (AASHTO T277), and corrosion resistance. Four groups of concrete mixtures that covered a wide range of materials and mixture proportions were included. Water/cementitious ratios used were 0.45, 0.38, and 0.33, corresponding to cementitious contents of 564, 658, and 752 lbs/cu yd, respectively. Different combinations of fly ash and silica fume were used. Fly ash content ranged between 10 and 50% by weight of the total cementitious material. Silica fume was included in proportions between 5 and 15%. Effects of fly ash and silica fume on strength and permeability of concrete and on corrosion of steel in concrete are discussed. Correlation is established between results of the Florida water permeability test and results of the AASHTO T277 chloride permeability test. It is also shown that concrete mixtures with equal compressive strengths do not necessarily produce equal levels of permeability, especially when fly ash and silica fume are included in the mixture. This lack of correlation continues until the strength reaches about 8,000 psi. At and beyond 8,000 psi, a well-defined trend is observed. With increased concrete strength, the permeability becomes consistently low to very low according to both AASHTO T277 and water permeability classifications. Findings from this phase of the research affirm the need to develop specifications for concrete durability based on requirements for both compressive strength and permeability of concrete.

3351
Attiogbe, E. K., Nmai, C. K., and Gay, F. T., "AIR-VOID SYSTEM PARAMETERS AND FREEZE-THAW DURABILITY OF CONCRETE CONTAINING SUPERPLASTICIZERS," Concrete International, Jul 1992, Vol. 14, No. 7, pp 57-61.

The air-void system parameters used as measures of freeze-thaw resistance are noted, and air-void spacing factor as a measure of freeze thaw durability is discussed. The effects of freezing rate, spacing factor equations, and deicer scaling are also covered. It is noted that properly air-entrained concretes containing superplasticizers can have adequate freeze-thaw resistance at calculated spacing factors greater than the ACI recommended maximum spacing factor of 0.008 in. Test data for concretes made with or without superplasticizers show that virtually all the concretes with adequate resistance under freeze-thaw testing had specific surface values less than the ACI recommended minimum.

3351a
Azizinamini, A., "PARAMETRIC STUDY OF VARIABLES AFFECTING TENSION DEVELOPMENT LENGTH IN HIGH STRENGTH CONCRETE," in Bond in Concrete: From Research to Practice, Proceedngs of the CEB International Conference held at Riga Technical University, Oct. 15-17, 1992, Riga, Latvia, Vol. 2, Topics 3-7, pp. 4-27 to 4-36.

High strength concrete with compressive strength in excess of 100 MPa is being used in building construction. Because of a lack of data the American building code, ACI-318-89, imposes an arbitrary upper limit of 69 MPa on fc', specified compressive strength of concrete, that may be used in calculating tension development length and tension splice length. A research study was conducted to evaluate the bond performance of reinforcing bars embedded in high strength concrete. Twelve beam splice specimens using No. 11 reinforcing bars and concrete with compressive strength exceeding 100 MPa were tested. The effects of several variables on bond capacity in high strength concrete are discussed.

3352
Baalbaki, W., Aitcin, P-C., and Ballivy, G., "ON PREDICTING MODULUS OF ELASTICITY IN HIGH-STRENGTH CONCRETE," ACI Materials Journal, Sep-Oct 1992, Vol. 89, No. 5, pp 517-520.

This paper reports on tests carried out on high-strength concrete made with a water-cementitious material ratio of 0.27. The test results indicate that the two-phase composite models used to predict Ec', and the relationship between Ec' and fc' , recommended by some codes, are no longer appropriate. The study illustrates how concrete elastic properties vary at high strengths.

3353
Baalbaki, W., Baalbaki, M., Benmokrane, B., and Aitcin, P-C., "INFLUENCE OF SPECIMEN SIZE ON COMPRESSIVE STRENGTH AND ELASTIC MODULUS OF HIGH-PERFORMANCE CONCRETE," Cement, Concrete and Aggregates, 1992, Vol. 14, No. 2, pp 113-117.

An experimental study of the influence of specimen size on compressive strength and static elastic modulus of high-performance concrete is reported. The elastic modulus was determined on the basis of surface strain of cylinders of two sizes made with the same volumetric mix proportions. The results show that the larger specimen has a lower compressive strength, and a higher elastic modulus. The paper presents relationships for calculating the compressive strength and elastic modulus of 150-mm cylinders from the values obtained on 100-mm cylinders.

3354
Boulay, C., Belloc, A., de Larrard, F., and Torrenti, J-M., "NEW METHOD OF SURFACING TEST SAMPLES OF HIGH AND VERY HIGH PERFORMANCE CONCRETE," Bulletin de Liaison des Laboratoires des Ponts et Chaussees, May-Jun 1992, No. 179, pp 43-55.

The authors describe investigations aimed at finding a simple and effective method of capping samples of high and very high performance concrete for compression tests. Three approaches are examined separately: the use of an epoxy resin mortar, an American technique consisting of interposing, between the test sample and the plates of the press, a neoprene disc confined in a metal box, and a new technique (the sand box) in which the neoprene is replaced by dry sand. These three methods are compared with the best known technique (grinding, which requires specific and costly equipment) and the conventional method for which a substitute is sought: capping with sulphur. The sand box is found to be the best substitute technique and the results it produces are comparable to those obtained with grinding in the case of high performance concrete (of strength between 50 and 80 MPa). Further work remains to be done to optimize the procedure and to enable the method to be standardized.

3355
Bridge, R. and Webb, J., "THIN WALLED CIRCULAR CONCRETE FILLED STEEL TUBULAR COLUMNS," in Composite Construction in Steel and Concrete II, Proceedings of an Engineering Foundation Conference, Potosi, MO, June 14-19, 1992; Ed. by Samuel Easterling and W. M. Kim Roddis; ASCE, New York, 1992, pp 634-649.

The thin walled steel tube filled with high strength concrete delivers the economies of a concrete column with the speed of construction and the constructability of a steel column resulting in significant economies in the overall cost of a building project. The use of an effective area to account for local buckling of the thin walled tubes has been verified by tests.

3356
Bruce, R. N., Russell, H. G., Roller, J. J., and Martin, B. T., "FEASIBILITY EVALUATION OF UTILIZING HIGH STRENGTH CONCRETE IN DESIGN AND CONSTRUCTION OF HIGHWAY BRIDGE STRUCTURES," Interim report, Louisiana Transportation Research Center, Baton Rouge, LA, 1992, xxii, 228 pp. (FHWA/LA-92/264; PB93-212140)

The objective of this investigation was to evaluate the feasibility of using high-strength concrete in the design and construction of highway bridge structures. A literature search was conducted; a survey of five regional fabrication plants was performed; mix designs were studied in the laboratory and in the field; and three series of tests consisting of a total of nine full-scale specimens were conducted. The first series included three pile specimens tested in flexure. Each of the pile specimens had a 24-in. (610-mm) square cross section with a 12-in. (305-mm) diameter void running its full length. All the pile specimens were 24 ft (7.31 m) long. The pile specimen concrete, at the time of testing, had an average compressive strength of 8,067 psi (55 MPa). The second series consisted of three full-size bulb-tee specimens. Flexural tests of two bulb-tee specimens are reported. The third specimen is being used for determination of long term static-load behavior. Results will be given in a separate report. The specimens were standard 54-in. (1,372-mm) bulb-tee sections with a 6 in. (152 mm) thick web. One of the test specimens had a slab 9 1/2 in. (241 mm) thick and 10 ft (3,048 mm) wide cast on top of it. The slab had an average concrete compressive strength of 4,037 psi (48 MPa). The second specimen was tested without a slab. The concrete of each bulb-tee specimen had an average 28-day compressive strength of 9,800 psi (68 PMa). Each girder specimen contained the same number and configuration of longitudinal prestressing strands and same amount of web reinforcement. Three shear tests are also reported. These shear tests were performed using the ends of the two flexural test specimens. Since the shear specimens were taken from the flexural specimens, they had the same cross-sectional configuration and concrete strength as the flexural specimens. The third series consisted of the fabrication and driving of a single 130-ft (38.6-m) pile specimen. The pile specimen had the same cross-sectional configuration as the pile specimens tested in the laboratory. The concrete of the pile specimen had an average 28-day compressive strength of 10,453 psi (72 MPa). A fourth series of tests is scheduled to be completed in the fall of 1993. This series of tests will consist of fatigue testing two full-size bulb-tee specimens. The results of the fatigue tests and the long-term behavior of specimen BT3 will be the subject of a separate report.

3357
Burg, R. G. and Ost, B. W., "ENGINEERING PROPERTIES OF COMMERCIALLY AVAILABLE HIGH-STRENGTH CONCRETES," Portland Cement Association, Skokie, IL, 1992, Research and Development Bulletin No. RD104.01T, 55 pp.

The report summarizes information from the first 19 months of a three year study of engineering properties of high-strength concrete. Six concretes in the range of 10,000 to 20,000 psi (69 to 138 MPa) were studied. Water-to-cement ratios ranged from 0.26 to 0.43; water-to-cementitious material ratios ranged from 0.22 to 0.32. The concretes containing either no mineral admixtures, silica fume only, or both fly ash and silica fume were delivered by a ready-mix supplier for laboratory tests. These tests included temperature rise of large cube specimens; compressive strength of cylinders, cores, and insulated specimens; static modulus of elasticity; tensile strength; modulus of rupture; thermal expansion; drying shrinkage; freezing and thawing durability; and water absorption. Specimens were also prepared for testing for creep, drying shrinkage, rapid chloride permeability, resistivity, corrosion rate, and petrographic analysis.

3358
Cohen, M. D., Zhou, Y., and Dolch, W. L., "NON-AIR-ENTRAINED HIGH-STRENGTH CONCRETE - IS IT FROST RESISTANT?" ACI Materials Journal, Jul-Aug 1992, Vol. 89, No. 4, pp 406-415.

Non-air-entrained high-strength concrete specimens with 0.35 water-cementitious materials ratio and 10 percent silica fume by mass of portland cement were cured for 7, 14, 21, and 56 days to evaluate the effects of the duration of curing in saturated lime-water prior to the freezing and thawing cycles on their frost resistance properties. The aggregates used in this investigation had a proven frost resistance. Therefore, the failure of the non-air-entrained concrete specimens could be attributed only to cracking of the paste. It was found that silica fume modified the frost resistance mechanism of the paste in the concrete. All specimens failed when tested in accordance to the ASTM C 666 Standard Test, Procedure A, using 60 percent relative modulus as the failure criterion. The data suggested the possible existence of a 14 to 21-day pessimum duration of curing in saturated lime-water, which was associated with the largest gains in length and mass, the largest drops in bulk density and compressive strength, and the lowest number of cycles to failure (or lowest durability factor). ASTM C 666, Procedure A appeared to be a viable test for evaluating the frost resistance of the concrete, even though the required 14-day curing duration prior to the freezing and thawing cycles, lying within the pessimum curing range, yielded conservative results. There were some improvements to the frost resistance properties when the duration of curing prior to the freezing and thawing cycles was reduced to 7 days or increased to 56 days, but the improvements were inadequate to enable the concrete to pass the standard test requirements. Thus, it is suggested that the failure of the specific non-air-entrained high-strength concrete tested in this investigation was due to inherent concrete properties, and not to the shortcoming of the ASTM C 666, Procedure A, standard test. An interesting observation was made when the dynamic moduli of the deteriorated specimens were compared to their compressive strengths. The damage induced in the mechanical property of the concrete after 300 cycles of freezing and thawing was mainly indicated by a significant drop in the moduli (i.e., down from 6.5 million psi at 0 cycles to 300,000 psi at 300 cycles). However, the compressive strengths did not show such a dramatic reduction. For instance, while the highest compressive strength was registered at about 11,000 psi at 0 cycles, the lowest was registered at about 8000 psi at 300 cycles. Even the lowest strength value still puts the concrete in the high-strength category. An explanation for this observation cannot be provided without further study of the microstructure, but it is clear that during the freezing and thawing cycles a stage had been reached in the concrete deterioration process when the conventional relationship between the moduli and the compressive strengths no longer appeared to hold true.

3359
Cook, W. D., Miao, B., Aitcin, P-C., and Mitchell, D., "THERMAL STRESSES IN LARGE HIGH-STRENGTH CONCRETE COLUMNS," ACI Materials Journal, Jan-Feb 1992, Vol. 89, No. 1, pp 61-68.

The influence of concrete strength on the thermally induced stresses during curing of three large-columns was investigated. Heat flow analyses, adjusted to match the measured temperatures, enabled the temperature distributions to be determined. Finite element analyses were carried out to investigate the risk of cracking due to stresses induced by the nonlinear thermal strains. The higher strength concretes did not result in larger maximum temperatures and had lower risks of cracking than the normal strength concrete used.

3360
Day, R. L., "THE EFFECT OF SECONDARY ETTRINGITE FORMATION ON THE DURABILITY OF CONCRETE: A LITERATURE ANALYSIS," Portland Cement Association, Skokie, IL, 1992, Research and Development Bulletin No. RD108.01T, 127 pp.

The report comprises a review and analysis of the available literature pertaining to the causes, effects and prevention of secondary (delayed) ettringite in concrete. Over 300 publications have been examined. Case studies of damage in concrete possibly caused by secondary ettringite formation are examined first. Fundamental research on secondary ettringite formation, its chemistry, and deposition mechanisms is then reviewed. Key investigations on the topic are analyzed in detail. Next, the potential importance of (a) method of heat-curing and (b) the chemistry of cement is outlined. In the final chapter, a rapid test for evaluation of potential secondary ettringite susceptibility (the "Duggan" test) is evaluated. The analysis indicates that there appears to be a potential for a secondary ettringite formation problem in North America; it is highly probable that secondary ettringite formation can lead to significant deterioration of heat-treated concrete. However, it is unlikely that secondary ettringite formation is, or will be, the sole mechanism responsible for premature deterioration. The critical factors that determine extent of damage due to secondary ettringite formation are (a) duration of delay period before heating the concrete; (b) severity of the heating and/or cooling regime; and (c) the SO3/Al2O3 ratio of the cement. There is no evidence that non heat-treated concrete is susceptible to this phenomenon. Further research and improvements to the Duggan test may result in the development of a useful standard test method to assess the long-term dimensional stability and durability of concrete.

3361
de Larrard, F. and Belloc, A., "ARE SMALL AGGREGATES REALLY BETTER FOR MAKING HIGH-STRENGTH CONCRETE?" Cement, Concrete and Aggregates, Summer 1992, Vol. 14, No. 1, pp 62-63.

This paper discusses the statement that 10 to 12 mm is the maximum size of aggregates preferable for making high-strength concrete. The discussion is supported by experimental data on eight concretes of normal-strength and high-strength mixes. The paper concludes that, in the range of mixes that can be made with the used components, crushed limestone aggregates, portland cement, silica fume, and superplasticizer, the classical theory still seems to apply: 20 to 25-mm maximum size aggregates lead to better performances and economy than smaller size aggregates.

3362
de Larrard, F., Saint-Dizier, E., and Boulay, C., "BEHAVIOUR AFTER FAILURE OF HIGH OR VERY HIGH PERFORMANCE REINFORCED CONCRETE UNDER COMPRESSION," Bulletin de Liaison des Laboratoires des Ponts et Chaussees, May-Jun 1992, No. 179, pp 11-20.

The authors deal with behaviour of elements of high or very high performance concrete (compressive strength above 60 MPa) incorporating transverse reinforcements, subjected to centred compression. Tests were carried out on a 110 MPa concrete and on a reference concrete, both reinforced at rates comprised between 0 and 3%. A special servo technique made it possible to control all the force-displacement curves. It was observed that the experimental curve of the very high performance samples have a vertical section after the peak. In the presence of reinforcements, the curve then descends to form a horizontal asymptote, when the sample is split into two sections sliding on each other. This observation led to the construction of a simple model of behaviour explicitly taking account of the phenomenon of localization of deformations up to failure. This model makes it possible to reproduce, fairly closely, other curves found in the literature, in the field of rates of moderate reinforcement. Finally it is shown that the pseudo-failure sensitivity of very high performance concrete under compression is simply due to the fact that after failure it is the force taken up by the transverse reinforcements which mainly determines the residual bearing capacity of the reinforced concrete element.

3363
Detwiler, G., "HIGH-STRENGTH SILICA FUME CONCRETE - CHICAGO STYLE," Concrete International, Oct 1992, Vol. 14, No. 10, pp 32-36.

Material Service Corporation has developed and commercially marketed high strength silica fume concrete (HSSFC) in the Chicago area. Continuing optimization of the mix design has resulted in full scale test placements of concretes with compressive strengths surpassing 20,000 psi (140 MPa).

3364
Dilly, R. L. and Abshire, M., "PULLOUT TESTING OF HIGH-STRENGTH CONCRETE MEMBERS," in Nondestructive Testing of Concrete Elements and Structures, Proceedings of Sessions Sponsored by the Engineering Mechanics Division of ASCE in conjunction with the Structures Congress, April 13-15, 1992, San Antonio, TX; Ed. by Farhad Ansari and Stein Sture; ASCE, New York, 1992, pp. 194-205.

An experimental investigation of a high-strength concrete mixture was undertaken to measure and evaluate pullout and compressive strength properties. Two columns, a slab, and cylindrical specimens were cast with a condensed silica fume, CSF, concrete mixture. This mixture achieved a 28 day strength in excess of 10,000 psi. At an age of three days, pullout tests were obtained from three elevations of each column; and at ages of 1, 3, 7, 14, 28 and 61 days, pullout test results were obtained from the slab, and cylindrical specimens were tested for strength. Although previous pullout strength investigations of cast vertical members report top-to-bottom strength differences when typical mixtures were used, the results of this investigation show that these differences may not occur when a member is cast with a CSF mixture. Statistical parameters corresponding to a linear regression analysis of pullout and compressive strength results show a relatively 'tight fit,' which indicates that the pullout test method can be applied toward evaluating and controlling the quality of concrete cast with high-strength mixtures.

3365
Douglas, E., Bilodeau, A., and Malhotra, V. M., "PROPERTIES AND DURABILITY OF ALKALI-ACTIVATED SLAG CONCRETE," ACI Materials Journal, Sep-Oct 1992, Vol. 89, No. 5, pp 509-516.

The purpose of this study was to formulate the proportioning of concrete mixes made with ground granulated blast furnace slag activated with sodium silicate, and to determine their properties and durability. Six mixes were made with a solution having silicate modulus Ms equals 1.47 and one mix with sodium silicate of Ms equals 1.22. All the mixes were air-entrained. Compressive and flexural strengths, Young's modulus of elasticity, shrinkage, and chloride ion penetration were determined. Measurements of length and mass changes, as well as resonant frequency and pulse velocity, were performed to evaluate the resistance of the concretes to repeated cycles of freezing and thawing. Sulfate resistance was evaluated by the same technique. The study shows that air content, volume of air-entraining admixture, slump, and early-age compressive strength are affected by the sodium silicate-slag ratio. Compressive and flexural strengths of the concretes at 7 days and beyond are comparable to or better than those of a portland cement concrete with equivalent water-cement ratio and workability. Drying shrinkage and expansion shrinkage strains were higher than those of a comparable portland cement concrete. Low sodium silicate-slag ratios adversely affected the resistance to repeated freezing and thawing cycles but improved the resistance to chloride ion penetration. Longer term test measurements are necessary to evaluate the resistance of the concretes to sulfate attack.

3366
Ellis, W. E., Jr., "FOR DURABLE CONCRETE, FLY ASH DOES NOT "REPLACE" CEMENT," Concrete International, July 1992, Vol. 14, No. 7, pp. 47-51.

It is noted that specifications governing the use of fly ash in concrete often do not allow for the full exploitation of fly ash in improving concrete properties. The article discusses concrete durability and how fly ash interaction improves durability. Sulfate resistance and alkali-silica reaction are discussed, as well as resistance to freezing and thawing and corrosion. Comments are made on the use of admixtures in concrete and the danger of too much cement.

3367
Ernzen, J. J. and Carrasquillo, R. L., "RESISTANCE OF HIGH STRENGTH CONCRETE TO COLD WEATHER ENVIRONMENTS," Interim Report; Center for Transportation Research, University of Texas, Austin, TX, 1992, Research Report No. 481-7, xxi, 304 p. (FHWA/TX-93-481-7; PB93-193647)

This report describes an experimental laboratory evaluation program which was conducted on several high strength concrete mix designs in order to ascertain the effects of various air entrainment levels in the short and long-term performance of high strength concrete. The project included comparisons in slump, strengths, freeze-thaw cycling performance, chloride ion penetration, permeability, deicer scaling, and microscopical air void analyses.

3368
Fagerlund, G., "EFFECT OF THE FREEZING RATE ON THE FROST RESISTANCE OF CONCRETE," Nordic Concrete Research, 1992, Publication No 11, pp 20-36.

A limited literature survey shows that there is no unique relation between the freezing rate in an unsealed test and the amount of frost damage. A theoretical analysis shows that the effect of the freezing rate on the destructive forces occurring during a sealed test is very limited, if any. This is also confirmed experimentally by tests in which the effect of the freezing rate on the critical degree of saturation is studied and found to be negligible. Therefore, the different and opposing effects of the freezing rate that have been observed in unsealed tests are no doubt mainly caused by the effect that the shape of the freeze/thaw cycle has on the maximum water content that is reached in the specimen during the test.

3369
Figg, J., "EARLY AGE PERMEABILITY MEASUREMENTS FOR PREDICTION OF CONCRETE DURABILITY," in Durability of Concrete: The G. M. Idorn International Symposium held at the 1990 Annual ACI Convention in Toronto, Ontario, Canada; Ed. by Jens Holm and Mette Geiker; American Concrete Institute, Detroit, MI, 1992, pp 289-303. (ACI SP-131)

Concrete prisms 500 x 100 mm were made using cement:aggregate proportions of 1:3, 1:6 and 1:9 with three different aggregates (flint gravel, limestone, basalt) and w/c ratios in the range 0.35 - 0.90. Drilled-hole (Figg) permeability measurements were made after the prisms had been cured under water for 28 days and conditioned at 20 degrees C and 65 percent RH. The samples were exposed outdoors in trays 50mm deep to accelerate damage from weathering in the expectation that the most permeable concretes would have the least good durability. After 10 years because the prisms were in remarkably good condition they were dried and the air permeabilities were remeasured. The prisms were then returned to the exposure trays. The most permeable concretes (basalt) suffered damage after 12 winters exposure. The permeability tests correctly predicted relative durability but the unexpectedly good performance of the specimens is attributed to complete compaction, thorough curing and continued access to water allowing further cement hydration.

3370
Giaccio, G., Rocco, C., Violini, D., Zappitelli, J., and Zerbino, R., "HIGH-STRENGTH CONCRETES INCORPORATING DIFFERENT COARSE AGGREGATES," ACI Materials Journal, May-Jun 1992, Vol. 89, No. 3, pp 242-246.

Concrete is an heterogeneous material whose properties depend on the properties of its component phases and the interactions between them. This paper reports a study of the effect of coarse aggregate characteristics on the mechanical properties of high-strength concretes. Granitic, basaltic, and calcareous aggregates were used. Compressive and flexural strength, modulus of elasticity, and stress-strain behavior were analyzed in concrete, mortar, and rocks. Matrix-aggregate bond strength is also evaluated.

3371
Guimaraes, G. N., Kreger, M. E., and Jirsa, J. O., "EVALUATION OF JOINT-SHEAR PROVISIONS FOR INTERIOR BEAM-COLUMN-SLAB CONNECTIONS USING HIGH-STRENGTH MATERIALS," ACI Structural Journal, Jan-Feb 1992, Vol. 89, No. 1, pp 89-98.

Current provisions for design of beam-column-slab connections are based primarily on results of tests of connections constructed with concrete strengths not exceeding 6000 psi and reinforcement with nominal yield strengths of 60 ksi or less. Results of tests conducted on 4 interior beam-column-slab connections constructed with combinations of normal and high-strength concrete and reinforcement are presented, and existing joint-shear provisions are evaluated for use in design of connections constructed with high-strength materials.

3372
Hakkinen, T., "THE MICROSTRUCTURE OF HIGH STRENGTH BLAST FURNACE SLAG CONCRETE," Nordic Concrete Research, 1992, Publication No 11, pp 67-82.

The microstructures of the blended cement concrete, alkali activated slag concrete and portland cement concrete were compared. The structures of the samples and the compositions of the hardening products were investigated by means of porosity studies, optical and scanning electron microscopy, thermoanalysis and X-ray studies. In the alkali-activated and auto-activated slag concrete the structure contains microcracks at the microscopic level. According to the SEM studies the hardened structure of alkali activated glassy slag is composed of smooth granular products, while the fibre type hardening products are lacking.

3373
Hakkinen, T., "THE PERMEABILITY OF HIGH STRENGTH BLAST FURNACE SLAG CONCRETE," Nordic Concrete Research, 1992, Publication No 11, pp 55-66.

The permeability properties of the high strength slag concrete were studied by means of carbonation tests, water suction and gas penetration. The permeability of the blended cement concrete was compared to that of the alkali activated slag concrete and portland cement concrete. According to the results the high strength slag concrete activated by cement is very dense. The carbonation results indicated that in high strength concrete the dense structure of the paste compensates for the lack of calcium in blended cement concrete. In the alkali activated slag concrete the structure contains microcracks at the microscopic level. The rate of carbonation was significantly higher in alkali activated slag concrete than in other concretes. The gas permeability results revealed the same tendencies as the carbonation tests. Water suction values were very low in all high strength concrete samples.

3374
Held, M. and Konig, G., "HIGH STRENGTH CONCRETE UP TO B 125 - A SUITABLE CONSTRUCTION MATERIAL FOR COMPRESSED MEMBERS SUBJECTED TO HIGH LOADS," Beton-und Stahlbetonbau, Feb 1992, Vol. 87, No. 2, pp 41-45.

The development and application of high-strength concrete types, characterized by cylinder compressive strengths of between 60 and 130 N/mm2, has increased considerably throughout the world over the past 15 years. Recent European guidelines, such as Norwegian standard NS 3473 and the CEB Model code 1990, deal with concrete types with compressive strengths up to strength class B 105. Consequently, the introduction of the Common European Market will bring with it increased use of high-strength concrete types in Germany also. The paper reports on new concrete technology and the mechanical properties of high-strength concrete. On the basis of a comparison of international standards, a proposal is presented for application of the compressive strength and the stress-strain relation for the compressed zone. In addition, a report is provided on the first column tests using high-strength concrete (B 85) at Darmstadt Technical University. In German.

3375
"HIGH STRENGTH CONCRETE," Compilation 17, American Concrete Institute, Detroit, MI, 1992, 96 pp.

This booklet is a compilation of articles on high strength concrete ranging from the production, mixture proportions, properties to case studies. The articles were previously published in the Institute's periodicals.

3376
Idorn, G. M., Johansen, V., and Thaulow, N., "RESEARCH INNOVATIONS FOR DURABLE CONCRETE," Concrete International, July 1992, Vol. 14, No. 7, pp. 19-24.

The article focuses on how the parallel developments in practice and research can be effectively integrated for improved quality management of concrete in production and for improved performance quality of field concrete. Concrete manufacturing technology is discussed, and the need is indicated for industrial process monitoring. The requirements for concrete durability research are discussed. Comments are made on ASTM specifications, with particular reference to ASTM C 33, Standard Specification for Concrete Aggregates, ASTM Specification C 618-91, and the test method ASTM C 311-90. It is noted that the nature of concrete during production and field performance must be the primary target for scientific and applied studies, and laboratory findings must be used with due regard to rational model laws.

3377
Jensen, H. E., "STATE-OF-THE-ART REPORT FOR HIGH STRENGTH CONCRETE SHRINKAGE AND CREEPING," Doctoral Thesis, Afdelingen for Baerende Konstruktioner, Technical University of Denmark, Lyngby, Denmark, 1992, 71 pp. (Text in Danish; Summary in English)

This is a qualitative analysis of the test results presented in the test report for time-dependent mechanical properties in concretes. The analysis concerns a qualitative evaluation of the general mechanical properties and the time-dependent properties shrinkage, creep, weight-loss, development of strength/stiffness, age at loading, stress/strength ratio, microcracking, drying creep, static-fatigue and creep recovery. Based upon the analysis it is demonstrated that high-strength/high-performance concrete, containing microsilica fume and/or fly-ash and plasticizer, is not a new material with respect to the investigated properties.

3377a
Kaku, T., Yamada, M., Iizuka, S., and Zhang, J., "A PROPOSAL OF BOND STRENGTH EQUATION FOR R. C. MEMBERS INCLUDING HIGH STRENGTH CONCRETE LEVEL," in Bond in Concrete: From Research to Practice, Proceedngs of the CEB International Conference held at Riga Technical University, Oct. 15-17, 1992, Riga, Latvia, Vol. 2, Topics 3-7, pp. 4-1 to 4-10.

Twenty six simply supported reinforced concrete beams were tested to investigate bond splitting strength of primary bars in a shear span. Test variables were concrete compressive strength, development length and spacing of primary bars, amount and detail of transverse reinforcement, and cross sectional dimension of the specimens. It was clear that the arrangement of supplementary ties was very effective in increasing the bond resistance. The bond strength difference between top and bottom bars reduced as the concrete strength was increased. Furthermore, a bond strength equation was proposed from the test results and compared with equations proposed by other Japanese investigators.

3378
Kankkunen, H. and Ojanen, P., "CONCRETE RHEOLOGY AND COMPACTION," Nordic Concrete Research, 1992, Publication No 11, pp 100-109.

The availability of good natural aggregates presents problems as locations have to be found where crushing and/or washing of aggregates is most economical. The higher quality requirements of high-strength concrete set more and more demands on aggregate quality. The influence of gap-graded curves has been investigated and positive features have been found so that it is possible to make use of aggregates with poorer quality. One field of this research consisted of investigating the influence of natural and crushed aggregates on concrete workability. When using crushed aggregate, the particle shape was the most important factor affecting concrete workability. This property was emphasized when using coarse aggregates. Situations where crushed aggregate can be used as the natural aggregate are discussed although the grading curve of fines and quantity of coarse aggregate are decisive for the usability of concrete. Usually when choosing crushed aggregate the content of water and cement becomes higher, but, by developing a crushing technique so that the particle shape is as round as possible, workability can be almost as good as for natural aggregate, and concrete strength even better.

3379
Kosmatka, S. H. and Panarese, W. C., "DESIGN AND CONTROL OF CONCRETE MIXTURES." 13th Edition, Portland Cement Association, Chicago, 1992, vii, 205 pp.

"Design and Control of Concrete Mixtures" has been the cement and concrete industry's primary reference on concrete technology for over 70 years. This fully revised and expanded edition was written to provide a concise, current reference on concrete and to include many advances in concrete technology that have occurred since the last edition. Besides presenting much new information, the 13th edition is more "user friendly" than previous editions. Chapters 1-5 include permeability and abrasion resistance of concrete; hot, blended, and expansive cements; cement strength and compound transformation; sea-dredged aggregate, recycled concrete, thermal properties of aggregate, alkali-aggregate reactivity; and an extended discussion on the effect of various concreting practices on air content. Chapters 6-10 have new sections on slag, fly ash, silica fume, corrosion inhibitors, superplasticizers, air detrainers, mix-design procedure including a flow chart, pumps, conveyor belts, high-energy mixers, overlays, vapor barriers, jointing, and the effect of temperature on time of set. New topics in Chapters 11-15 include evaporation retarders, modulus of elasticity, Poisson's ratio, shear strain, chemical volume changes, carbonation, high- and low-temperature effects, cast-in-place test cylinders and other new quality control and investigative test procedures, and special types of concrete such as lightweight, heavyweight, high-strength, roller-compacted, porous, polymer-modified, and mass concrete. Most of the new or expanded material is accompanied by explanatory photos, tables, or graphs. A new appendix includes frequently needed metric conversion tables and a comprehensive list of cement- and concrete-related ASTM standards. An index is provided.

3380
Lahlou, K., Aitcin, P-C., and Chaallal, O., "BEHAVIOUR OF HIGH-STRENGTH CONCRETE UNDER CONFINED STRESSES," Cement and Concrete Composites, 1992, Vol. 14, No. 3, pp 185-193.

This paper presents the preliminary results of an experimental investigation on confined high-strength concrete, which is ongoing in the Civil Engineering Department of the Universite de Sherbrooke. The behaviour of confined concrete at three 28-day strength levels was investigated (47, 78 and 115 MPa). Both the standard compressive strength and the tensile splitting strength were determined. Three types of lateral confinement were used: a) lateral hydrostatic pressure (Hooke triaxial cell); b) steel tubes; and c) glass fibre tubes. Three types of cement were used, one of which contained silica fume. The superplasticizer used was a sodium salt of a polycondensate of formaldehyde and naphthalene. Details of the mix design used are provided. All tests on the confined specimens were done using a 3000 kN Material Testing System (MTS) machine. The axial strains were measured using two linear velocity displacement transducers. Strain gauges were used for lateral strain measurement. The results of the present preliminary study limited to concentrically loaded short circular columns show that: (1) confining high-strength concrete in a steel tube greatly increases its strength and results in outstanding new ultrahigh- strength concrete; (2) confining high-strength concrete in a steel tube improves its ductility, and (3) the confinement efficiency slightly increases with concrete compressive strength.

3381
Lane, D. S., "ALKALI-SILICA REACTIVITY. AN OVERVIEW OF A CONCRETE DURABILITY PROBLEM," in Materials: Performance and Prevention of Deficiencies and Failures, Proceedings of the Materials Engineering Congress, Aug 10-12, 1992, Atlanta, GA; Ed. by Thomas D. White; ASCE, New York, 1992, pp 231-244.

An overview of the problem of alkali-silica reactivity (ASR) is presented. It is a chemical reaction that can occur between aggregates containing certain forms of silica and the alkaline pore solution in concrete. The reaction mechanics are described and evaluation of aggregates as well as control of alkalines are considered. Recent research has identified additional forms of reactive silica, and some promising new screening tests have been developed as well as a rapid method for determining whether concrete has been affected by ASR. A considerable body of data attests to the effectiveness of ground granulated blast-furnace slag and pozzolans such as fly ash and silica fume to control deleterious reactivity in concrete.

3382
Lessard, M., Sarkar, S. L., Ksinsik, D. W., and Aitcin, P-C., "LONG-TERM BEHAVIOR OF SILICA FUME CONCRETE," Concrete International, Apr 1992, Vol. 14, No. 4, pp 25-30.

The experimental sidewalk, constructed in autumn 1980 in the SKW silicon plant in Becancour in Quebec province, Canada represents one of the first reported field applications of silica fume concrete in North America. The 11 sidewalk sections each have a different cement content, and silica fume additions ranged from 10 to 20 percent in addition to the cement content. The experimental sidewalk has been continually exposed to the extremely severe climatic conditions that prevail in Quebec province. An evaluation is made of experimental results.

3383
Lin, C-H., Ling, F-S., and Hwang, C-L., "FLEXURAL BEHAVIOR OF HIGH STRENGTH FLY ASH CONCRETE BEAMS," Journal of the Chinese Institute of Engineers, Taiwan, Jan 1992, Vol. 15, No. 1, pp 85-92.

The minimum void concept was used to proportion high strength fly ash concrete. Numerous trial batches were made to determine the optimum mix proportion. Nine beams were cast from optimum mix to investigate the flexural behavior of this type of concrete. The requirements specified in current ACI 318 for modulus of elasticity of concrete, modulus of rupture of concrete, flexural strength of beam sections, effective moment of inertia of flexural members, maximum tension reinforcement ratio and minimum tension reinforcement for seismic design were examined for their application to high strength fly ash concrete.

3384
Locoge, P., Massat, M., Ollivier, J. P., and Richet, C., "ION DIFFUSION IN MICROCRACKED CONCRETE," Cement and Concrete Research, Mar-May 1992, Vol. 22, Nos. 2-3, pp 431-438.

The influence of concrete microcracking state on transport by diffusion was studied for three different species: 3H, 137Cs and Cl-. No influence has appeared for tritium and cesium. A correlation was found between the transfer of chlorides and the specific microcracking surface.

3385
Luping, T. and Nilsson, L-O., "CHLORIDE DIFFUSIVITY IN HIGH STRENGTH CONCRETE AT DIFFERENT AGES," Nordic Concrete Research, 1992, Publication No. 11, pp 162-71.

The chloride diffusivity in high strength concrete blended with and without silica fume was determined at different ages by using a rapid method recently developed by the authors of this paper. The quantitative relations between diffusivity and curing age were obtained and expressed by a regression equation. The chloride penetration was evaluated and discussed by applying Fick's law taking diffusivity as the age dependent variable.

3386
Luping, T. and Nilsson, L-O., "RAPID DETERMINATION OF THE CHLORIDE DIFFUSIVITY IN CONCRETE BY APPLYING AN ELECTRICAL FIELD," ACI Materials Journal, Jan-Feb 1992, Vol. 89, No. 1, pp 49-53.

A mathematical model of ion diffusion under the action of a constant electrical field was established and the exact analytical solution of the differential equation in the model was found by considering semi-infinite diffusion. The relationship between the effective diffusion coefficient and the depth of chloride penetration under the action of an electrical field was derived. A simple method for penetrating chlorides into concrete was proposed so that the chloride penetration profiles and depths could be obtained in a very short time. The chloride diffusivities in cement pastes and mortars with various water-cement ratios were determined by the proposed method as well as with conventional diffusion cells, which took months to perform. The experimental results reveal good correspondence with other researchers' findings, and imply the possibility of evaluating chloride diffusivity in high-performance concrete and predicting chloride penetration into concrete structures in the field by short-term measures.

3387
Meletiou, C. A. and Tia, M., "PERMEABILITY EVALUATION OF CONCRETE BRIDGE STRUCTURES EXPOSED TO MARINE ENVIRONMENT IN FLORIDA (WITH DISCUSSION AND CLOSURE)," Transportation Research Record, 1992, No. 1371, pp 37-46.

A field permeability test (FPT) apparatus and method were developed and evaluated in both the laboratory and the field. The developed prototype FPT apparatus and method were used in the testing and evaluation of in-service marine structures in conjunction with other standard tests. The developed FPT apparatus and method appear promising in providing a suitable measuring system for the rapid, convenient, and reliable determination of the in situ water permeability of structural concrete. There appears to be a linear relationship between the charge (in coulombs) passed through a concrete material as measured by the rapid chloride permeability test (AASHTO T277-83) and its corresponding water permeability, with a coefficient of determination, R squared, of 0.90. There was an apparent relationship between permeability and durability of concrete in service. The concrete material that exhibited durability problems also demonstrated high permeability. The FPT method was demonstrated to be able to provide a relative measurement of permeability that can be used as an indication of the quality and performance characteristics of structural concrete.

3388
Millard, S. G. and Gowers, K. R., "RESISTIVITY ASSESSMENT OF IN-SITU CONCRETE: THE INFLUENCE OF CONDUCTIVE AND RESISTIVE SURFACE LAYERS," Proceedings of the Institution of Civil Engineers, Structures and Buildings, Nov 1992, Vol. 94, No. 4, pp 389-396.

Measurement of the electrical resistivity of concrete is a non-destructive technique that may be used in conjunction with potential mapping as a means of evaluating the severity of reinforcement corrosion. Concrete resistivity can be determined by placing four equi-spaced electrodes in contact with the structure to be measured, and passing an alternating current between the outer electrodes. Measuring the potential difference across the inner electrodes enables the resistivity to be calculated. A source of practical difficulty in measuring the resistivity in this way is the error caused by a surface layer with a resistivity lower or higher than that of the underlying concrete. This might be the result of, for example, salt ingress or carbonation of the surface. The effect is analyzed experimentally and theoretically, and practical correction curves are given, which permit an assessment of the true resistivity of the underlying concrete. Substantial error can be caused where there is a second surface layer with a relatively low resistivity on top of a high resistivity surface layer. This can occur, for example, with surface wetting of carbonated concrete. This low resistivity layer can cause a paradoxical increase in the resistivity measurement. The reasons for this effect are discussed, and practical guidance for in-situ resistivity measurement is given.

3389
Montgomery, F. R., Basheer, P. A. M., and Long, A. E., "INFLUENCE OF CURING CONDITIONS ON THE DURABILITY RELATED PROPERTIES OF NEAR SURFACE CONCRETE AND CEMENT MORTARS," in Durability of Concrete: The G. M. Idorn International Symposium held at the 1990 Annual ACI Convention in Toronto, Ontario, Canada; Ed. by Jens Holm and Mette Geiker; American Concrete Institute, Detroit, MI, 1992, pp 127-138. (ACI SP-131)

Good curing is now recognized as essential to achieving good durability of concrete and other cementitious material surfaces. However, it has not been easy to judge whether or not it has been achieved on site, so surface failures continue to occur. The Department of Civil Engineering at the Queen's University of Belfast has developed a number of test techniques to allow the measurement of surface strength, surface absorption and permeability, and surface abrasion resistance of structures on site. These have been used to assess the performance of various curing regimes for concrete and mortar, firstly to see if the test methods can make meaningful measurements of durability related properties and secondly to get an indication of the magnitude of the changes in these properties for different curing regimes and water cement.

3390
Mor, A., "HIGH-PERFORMANCE CONCRETE BECOMING A PRACTICAL OPTION," Concrete Construction, May 1992, Vol. 37, No. 5, pp 351-353.

A survey of the advantages offered by novel mix proportions for high-performance concretes is given. This term was coined to describe a material that not only has high strength, but also significantly higher stiffness, less volume change, and lower permeability.

3391
Mor, A., "STEEL-CONCRETE BOND IN HIGH-STRENGTH LIGHTWEIGHT CONCRETE," ACI Materials Journal, Jan-Feb 1992, Vol. 89, No. 1, pp 76-82.

The objective of this test program was to study the effect of condensed silica fume (CSF) on the mechanical properties of high-strength concrete made with lightweight aggregate (LWA), and compare these properties to concretes with similar strength properties. The tensile strength (modulus of rupture R), modulus of elasticity (Ec), stress-strain properties, and bond slip of reinforcing bars were studied for four concrete mixes of similar high strength [10,000 psi (69 MPa)] achieved through varying contents of CSF (0 and 13 to 15 percent by weight of cement) and low water-cement ratios (0.25 to 0.34). The use of CSF did not significantly change the ratio of compressive strength to Ec for concretes made from either aggregate, but it doubled the steel-concrete bond strength-compressive strength ratio at 0.01 in. (0.25 mm) slip for LWA concrete, while having no significant effect on normal weight aggregate (NWA) concrete. CSF reduced porosity and thickness of the transition zone adjacent to the steel, thus improving the adhesion-type bond at small slip levels. The lower Ec of LWA concrete, combined with its compatible aggregate and cement paste matrix, results in better utilization of the bond adhesion, allowing larger stress and strain levels.

3392
Mor, A., Gerwick, B. C., Jr., and Hester, W. T., "FATIGUE OF HIGH-STRENGTH REINFORCED CONCRETE," ACI Materials Journal, Mar-Apr 1992, Vol. 89, No. 2, pp 197-207.

The results of low-cycle fatigue testing of high-strength concrete are presented. Lightweight and normal weight aggregate concretes were tested under reversible loading under both submerged and air-dry conditions. Fatigue capacity of lightweight aggregate concrete was similar to or better than that of normal weight aggregate concrete of similar strength properties. Submersion of high-strength concrete in water did not affect its fatigue capacity. Fatigue capacity of high-strength reinforced concrete was found to be directly related to the bond between concrete and reinforcement and not related to any other strength property. The addition of silica fume to lightweight aggregate concrete improved its bond by 100 percent and its fatigue life by over 60 percent. No significant improvement was observed when silica fume was added to normal weight aggregate concrete. Results of extensive tests on accompanying specimens and post failure tests on the beams are presented.

3393
Murota, T., Hiraishi, H., Kaminosono, T., Teshigawara, M., Shiohara, H., and Fujitani, H., "DEVELOPMENT OF ADVANCED REINFORCED CONCRETE BUILDINGS USING HIGH-STRENGTH CONCRETE AND REINFORCEMENT. RESEARCHES ON STRUCTURAL PERFORMANCE CONDUCTED IN 1991," NIST Special Publication, Sep 1992, No. 843, pp 337-357.

A five-year National Project has been promoted by the Ministry of Construction of Japan since 1988 to develop such structures as super high-rise reinforced concrete buildings using high strength and high-quality concrete and reinforcing steel. The project is simply referred to as 'New RC'. This paper describes the outlines of some research subjects which were conducted in 1991 relative to structural performance.

3394
Naik, T. R. and Hassaballah, A. S., "USE OF THE BREAK-OFF METHOD FOR THE EVALUATION OF HIGH PERFORMANCE CONCRETE," in Materials: Performance and Prevention of Deficiencies and Failures, Proceedings of the Materials Engineering Congress, Aug 10-12, 1992, Atlanta, GA; Ed. by Thomas D. White; ASCE, New York, 1992, pp 92-106.

The Break-Off test is one of the recent developments for testing in-place concrete strength. This research was undertaken to investigate the reliability of the Break-Off test as a measure of the in-place strength of 8000 psi concrete. This high performance concrete is generally used in highly stressed precast or post-tensioned members, in high rise buildings, and/or in severe exposure conditions. To achieve this objective, the following parameters were investigated: aggregate shape; slab thickness; and, method of obtaining the cylindrical Break-Off test specimens, either by inserting a sleeve in the fresh concrete or by drilling a cylindrical core after the concrete has hardened. It is concluded that the Break-Off method can estimate with good correlation the in-place compressive strength of high-strength concrete.`

3395
Neeley, B. D., McDonald, W. E., and Lloyd, M. K., "INVESTIGATION OF PROPRIETARY AIR-ENTRAINING ADMIXTURES TO PRODUCE FROST-RESISTANT CONCRETE WITH LOW AIR CONTENT." Final Report, U. S. Army Engineer Waterways Experiment Station, Vicksburg, MS, 1992, 50 pp. (WES/TR/SL-92-6; AD-A248-959)

This report covers a laboratory investigation of six air-entraining admixtures (AEAs) to determine whether adequate frost resistance could be achieved in concrete with a water-cement ratio not exceeding 0.50 and air content less than the minimum value currently recommended by the American Concrete Institute. Concrete mixtures were proportioned and tested for resistance to freezing and thawing according to the provisions of ASTM C 666, Procedure A as required by ASTM C 233. Durability factors were determined according to the provisions of ASTM C 666. Values for spacing factors and specific surfaces of the air-void systems were measured according to the provisions of ASTM C 457. When different AEAs were tested, the results indicated a significant difference in the frost resistance of concretes having the same air content. The AEAs with high air content provided adequate frost resistance; one AEA with medium air content provided adequate frost resistance; none of the AEAs with low air content provided adequate frost resistance.

3396
Nilsen, A. U. and Aitcin, P-C., "PROPERTIES OF HIGH-STRENGTH CONCRETE CONTAINING LIGHT-, NORMAL-, AND HEAVYWEIGHT AGGREGATE," Cement, Concrete, and Aggregates, Summer 1992, Vol. 14, No. 1, pp 8-12.

The results are presented of a study of the influence of density of aggregate on mechanical properties of high-strength concrete. The materials used and the experimental details are described, and the results are discussed. Lightweight concretes and heavyweight concretes were studied. A comparison of the experimentally determined values of the elastic modulus with the calculated values according to the relationships recommended by the ACI Building Code, the British Standard Code, and the Norwegian Standard Code, showed that all codes overestimated the elastic modulus of high-strength heavyweight concrete. In general, the magnitude of drying shrinkage was inversely proportional to the period for which specimens were water cured. These and other study findings are discussed.

3397
Nilsen, A. U. and Aitcin, P-C., "STATIC MODULUS OF ELASTICITY OF HIGH-STRENGTH CONCRETE FROM PULSE VELOCITY TESTS," Cement, Concrete, and Aggregates, Summer 1992, Vol. 14, No. 1, pp 64-66.

Since the measurement of the pulse velocity is very easy and a correlation exists between the static modulus of elasticity and the stiffness constant from the pulse velocity test, this study uses the latter for predicting the static modulus of elasticity of high-strength concretes with very different elastic properties. Because the test is nondestructive, it is possible to do a continuous measurement of the elastic properties of the concrete, requiring no extra material and manpower.

3398
Nmai, C. K., Farrington, S. A., and Bobrowski, G. S., "ORGANIC-BASED CORROSION-INHIBITING ADMIXTURE FOR REINFORCED CONCRETE," Concrete International, April 1992, Vol. 14, No. 4, pp. 45-51.

This paper describes a unique organic-based corrosion-inhibiting admixture (OCIA), which is a combination of amines and esters in a water medium, for corrosion protection of reinforcing steel in concrete. The corrosion protection mechanism of OCIA, and the effects of OCIA on the plastic and hardened properties of concrete are discussed. The performance characteristics of OCIA were evaluated by two different time-to-corrosion tests. The recommended dosage for OCIA is 1 gal/yd3 (5.0 l/m3) of concrete.

3399
Ollivier, J. P. and Massat, M., "PERMEABILITY AND MICROSTRUCTURE OF CONCRETE. A REVIEW OF MODELLING," Cement and Concrete Research, Mar-May 1992, Vol. 22, No. 2-3, pp 503-514.

Models are presented as an analysis tool for prediction of permeability in cracked concrete and thus the durability of concrete. A modeling approach is presented in which porous characteristics are related to concrete permeability.

3400
Ozyildirim, C., "EFFECT OF CALCIUM NITRITE ON THE PROPERTIES OF CONCRETE USED IN PRESTRESSED PILES AND BEAMS." Final Report, Virginia Transportation Research Council, Charlottesville, VA, 1992, 19 pp. (FHWA/VA-93-R5; VTRC-93-R5; PB93-189843)

This study evaluates the concretes in steam-cured prestressed piles and beams containing calcium nitrite as protection against chloride-induced corrosion of the steel strands and assesses their field performance over a 3-year period. Concretes containing slag were also included in the study to evaluate their permeability to chloride ions. It was found that concretes containing calcium nitrite (DCI) have satisfactory strengths and are expected to provide adequate resistance to cycles of freezing and thawing. The steam-cured slag concretes were found to have lower permeability than the similar portland cement concretes. Since the addition of DCI does not have an appreciable adverse effect on the properties of steam-cured concretes and has the potential to provide long-term protection against corrosion, its use is recommended in prestressed concrete subjected to severe exposure. The limited time available for laboratory and field testing did not allow conclusions on the effectiveness of the corrosion inhibitor. Continuing evaluations are recommended.

3401
Pfeifer, D. W., Perenchio, W. F., and Hime, W. G., "A CRITIQUE OF THE ACI 318 CHLORIDE LIMITS," PCI Journal, Mar-Apr 1992, Vol. 37, No. 2, pp 68-71.

Allowable chloride limits for new concrete, as outlined by the American Concrete Institute's Committee 318 in its Building Code, have been established since 1983. However, they do not appear to be consistent with current corrosion technology. This paper traces the changes in the requirements for chloride ion and suggests new limits based on the results of recent studies. Research is urgently needed to correlate the initiation of corrosion with "effective or threshold chloride", as measured by procedures that discount chloride tied up in aggregate and possibly in the cement paste. Studies must be made to determine why the threshold chloride level is apparently so different for deformed reinforcing bar and 7-wire prestressing strand.

3402
Pitt, J. M., Carnazzo, R. A., Vu, J., and Seshadri, M., "CONTROL OF CONCRETE DETERIORATION DUE TO TRACE COMPOUNDS IN DEICERS." Final Report, Engineering Research Institute, Iowa State University, 1992, 85 pp. (ISU-ERI-Ames-92229)

This report contains work on three facets of rock salt deicer action on freeze-thaw resistance of portland cement concrete. The first deals with improvement of mortars where it is demonstrated that a 10 to 15% replacement of cement with fly ash can more than double the life of concrete by reduction of porosity and stabilization of calcium hydroxide. Excessive fly ash was found to counter this benefit. Secondly, this research defines behavior and performance of aggregates displaying different service lives in concrete subjected deicers. Freeze-thaw in water produced failure in the aggregate while in deicers damage was exclusive to the mortar-aggregate interface or the mortar. Aggregate porosity appeared to be a good but not infallible predictor of concrete service life. Low porosity aggregates were best. The third feature of this research was development of a test method capable of modeling the freeze-thaw process and predicting life performance. This was done by adaptation of the ASTM C 666 test to include a reliability based design. Essential to this test method was objective definition of failure and a realistic model linking laboratory tests to the temperature environment observed in the field. The methodology was compared to performance of a pavement in central Iowa. The model predicted life of 25 years while the pavement failed at 26 years. This predictive method was also used to contrast the life of a pavement subject to different deicing materials as follows: no deicer-life = 25 years, low sulfate NaCl-life = 19 years, and high sulfate NaCl-life = 14 years.

3403
Pitt, J. M., Seshadri, M., and Covey, D. L., "RELIABILITY-BASED DESIGN FOR FREEZE-THAW CONCRETE," in Materials: Performance and Prevention of Deficiencies and Failures, Proceedings of the Materials Engineering Congress, Aug 10-12, 1992, Atlanta, GA; Ed. by Thomas D. White; Atlanta, GA; ASCE, New York, 1992, pp 462-475.

Observation of pavements in Iowa shows results from the test for freezing and thawing of concrete, ASTM C-666, is not always consistent with field performance. Similar concrete made with coarse aggregates from different sources have the same durability factor but demonstrate service lives differing by as much as ten years. ASTM C-666 was intended to provide a relative measure of concrete serviceability and makes no attempt at predicting service life, particularly when deicers are used. This paper presents preliminary research aimed at applying reliability analysis to estimate time to failure of concrete subject to frost action. Four carbonate aggregates with service lives ranging from ten to thirty years were tested by embedding randomly selected single stones in the neck of dog-boned shaped mortar briquettes with the mortar being proportioned to represent paving concrete. These specimens were subjected to cyclic freeze-thaw in water and deicing brine until failure. Failure was defined as rupture by gravity when specimens were lifted for inspection. Failure was observed to occur by one of three mechanisms: the aggregate itself, the bond between aggregate and mortar phases, and the mortar itself. When tested in water, failure tended to be aggregate dependent, except in one case where the aggregate outlasted the mortar. When tested in deicers, failure occurred at the bond, regardless of aggregate type. Test interpretation involves plotting cumulative failures vs. the number of cycles to failure, which gives a failure rate and expected number of cycles to failure. General trends include a dormant period before any failures occur, and varying rates of failure depending on aggregate source and test fluid. Deicers reduced expected cycles to failure and increased failure rate.

3404
Rangan, B. V. and Joyce, M., "STRENGTH OF ECCENTRICALLY LOADED SLENDER STEEL TUBULAR COLUMNS FILLED WITH HIGH-STRENGTH CONCRETE," ACI Structural Journal, Nov-Dec 1992, Vol. 89, No. 6, pp 676-681.

The results of tests performed on nine eccentrically loaded slender steel tubular columns filled with high-strength concrete are reported. The test parameters were the slenderness ratio and the eccentricity of axial thrust. A simple method to calculate the strength of columns is presented. The method shows good correlation with the test results reported in the paper as well as with those available in the literature.

3405
Ravindrarajah, R. S., "EVALUATION OF COMPRESSIVE STRENGTH FOR HIGH-STRENGTH CONCRETE BY PULSE VELOCITY METHOD," in Nondestructive Testing of Concrete Elements and Structures, Proceedings Sponsored by the Engineering Mechanics Division of ASCE in Conjunction with the Structures Congress, April 13-15, 1992, San Antonio, TX; Ed. by Farhad Ansari and Stein Sture; ASCE, New York, 1992, pp. 115-126.

Development of compressive strength and pulse velocity for high-strength concrete from the age of 5 hours are studied in relation to cementitious material types and curing conditions. Normal portland cement, blast-furnace slag cement and silica fume are used individually or in combination. Results show that: a) silica fume in concrete increases the pulse velocity; b) pulse velocity and strength are lower for air-cured concrete than for water-cured concrete; and c) the relationship between strength and pulse velocity is given by an exponential curve which is less influenced by curing or cementitious material types. Evaluation of in-situ concrete strength based on paste efficiency concept is examined.

3406
Roy, D. M., Shi, D., Scheetz, B., and Brown, P. W., "CONCRETE MICROSTRUCTURE AND ITS RELATIONSHIPS TO PORE STRUCTURE, PERMEABILITY, AND GENERAL DURABILITY." in Durability of Concrete: The G. M. Idorn International Symposium held at the 1990 Annual ACI Convention in Toronto, Ontario, Canada; Ed. by Jens Holm and Mette Geiker; American Concrete Institute, Detroit, MI, 1992, pp 139-152. (ACI SP-131)

The principal mechanism for the deterioration of concrete is transport of fluids either into or out of the pore structure of hardened body. The fluid transport occurs via a complex network of interconnected porosity incorporating both the cementitious matrix and matrix/aggregate interfacial regions. This paper describes the development of an experimental method and a mathematical background for a rapid water permeability measurement method and a mathematical model relating porosity, described in terms of a log-normal distribution, to permeability.

3407
Samarai, M. A., Sarsam, K. F., Kamaluddeen, N. M., and Al-Khafagi, M., "INFLUENCE OF TEMPERATURE, DRYING AND CURING METHOD ON PROPERTIES OF HIGH STRENGTH CONCRETE," in Concrete in Hot Climates, Proceedings of the 3rd International Conference held by RILEM, Sept 21-25, 1992, Torquay, England; Ed. by M. J. Walker; 1st ed.; E & FN Spon, London, 1992, pp 65-80.

In this work the influence of mix temperature and/or relative humidity (RH) is studied for HSC (high strength concrete). This is the second paper in a programme intended to study HSC behaviour in hot and dry environment. Research indicates similarities as well as differences in the influence of environment on HSC and NSC (normal strength concrete). Mix temperature rise is found to be harmful to both tensile and compressive strengths of concrete, tested wet or dry. Mix temperature influences the compressive strength of HSC by only 55% of the value obtained previously by others for NSC. The compressive strength of NSC and HSC rises significantly under short-term and long-term drying. However, HSC has a significantly smaller increase in compressive strength upon drying than NSC. Specimens cured in water up to the age of 28 days followed by drying exhibit sharply different effects of drying between compressive and tensile strengths. Short-term exposure to dry environment lowers the tensile strength of concrete. However, long-term drying with complete desiccation leads to an insignificant rise in tensile strength. This supports the conclusion, at this stage, that complete drying is not harmful to concrete tensile strength both for HSC and NSC. Elevated temperature curing raises HSC compressive and tensile strengths. However, this influence becomes less significant for higher strength concrete. Air curing beyond the age of 1 day has two contrasting effects on concrete strength. Compressive strength drop because of air curing becomes smaller for higher strength concrete. However, tensile strength drop due to air curing becomes more significant with stronger concrete. This contrast indicates the need for further research on the subject with a larger range of concrete strength.

3408
Sandvik, M. and Gjorv, O. E., "HIGH CURING TEMPERATURES IN LIGHTWEIGHT HIGH-STRENGTH CONCRETE," Concrete International, Dec 1992, Vol. 14, No. 12, pp 40-42.

A large scale field investigation is reported that attempted to provide realistic curing conditions in a study of the effect of elevated curing temperatures on high-strength concrete. The details of the experiment are described, and the results are presented and discussed. It was found that curing temperatures of up to 85 deg C did not adversely affect the mechanical properties of the concrete. Actually, a slight increase in compressive strength was observed. No detrimental effects in terms of microstructure or cracking of the elevated temperatures could be detected by thin section analysis. These and other findings are discussed.

3409
Saricimen, H., Maslehuddin, M., Al-Mana, A. I., and Eid, O., "EFFECT OF FIELD AND LABORATORY CURING ON THE DURABILITY CHARACTERISTICS OF PLAIN AND POZZOLAN CONCRETES," Cement and Concrete Composites, 1992, Vol. 14, No. 3, pp 169-177.

The environmental conditions in the Arabian Gulf countries are classified as aggressive and severely corrosive. Field and laboratory studies have shown that concrete in this region should be designed not only for strength but also for durability. Utmost emphasis should be given to produce dense and impermeable concrete, to extend the service life of structures. In this study, concrete samples were prepared using various types of cements and fly ashes at various mix designs. The samples were cured both in the field and in laboratory conditions. The permeability was determined by volume of permeable voids and absorption tests. The results showed that continuous water curing is necessary to obtain the least permeable concrete for both plain and pozzolan concretes. Irrespective of curing procedure followed, the fly ash concrete exhibited lower permeability than plain concrete for an initial test period of 7 days during curing. The fly ash concrete samples cured in the laboratory exhibited lower initial surface absorption than control concretes after 90 days of curing for all fly ash additions (10-40%) and cement factors (275-450 kg per cubic metre) used.

3410
Sarsam, K. F. and Al-Musawi, J. M. S., "SHEAR DESIGN OF HIGH- AND NORMAL STRENGTH CONCRETE BEAMS WITH WEB REINFORCEMENT," ACI Structural Journal, Nov-Dec 1992, Vol. 89, No. 6, pp 658-664.

This work examines 14 beams with stirrups failing in shear, in addition to 107 from the literature. These include high-strength (HSC) beams and normal strength concrete (NSC) beams. It is shown that using ACI Building Code Equation for concrete contribution is conservative for both HSC and NSC over a wide range of the principal variables; concrete compressive strength; stirrup nominal strength; longitudinal steel ratio; and shear span-to-depth ratio. However, a higher coefficient of variation (COV) is obtained using the more conservative Canadian code simple design alternative. A proposed design method is also discussed that is conservative with a lower COV than the ACI Equation.

3411
Scanlon, J. M., "ADMIXTURES - WHAT'S NEW ON THE MARKET." Concrete International, Oct. 1992, Vol. 14, No. 10, pp. 28-31.

The use of both mineral and chemical admixtures can greatly increase the ability of concrete to resist the corrosion of embedded metals. Fly ash is a major contributing partner in developing cost-effective, corrosion-resistant concrete. Innovations in mineral admixtures should provide the capability of obtaining exceptionally high strengths and moduli of elasticity, plus greater abilities to produce more impervious and corrosion-resistant concrete.

3412
Setunge, S., Attard, M. M., and Darvall, P. Le P., "ULTIMATE STRENGTH CRITERION FOR VERY HIGH STRENGTH CONCRETE SUBJECTED TO TRIAXIAL LOADINGS," Department of Civil Engineering, Monash University, Clayton, Victoria, Australia, Civil Engineering Research Report, No. 1/1992, 36 pp.

In recent years a considerable amount of research work has been carried out on the mechanical and structural properties of high strength concrete. The most common application of high strength concrete has been in heavily loaded columns of multistory structures. Accordingly several investigations were directed at studying the strength and ductility of high strength concrete columns confined with lateral ties or spirals. Concretes investigated had compressive strengths up to 90 MPa. Conclusions made in the above studies regarding the peak axial strength under confinement are not consistent. The work reported herein presents the results of an investigation into the behaviour of very high strength concrete subjected to triaxial loadings, in order to establish a failure criterion for concretes with compressive strengths in the range of 90 to 130 MPa subjected to a uniform lateral confinement. The influence of the type of coarse aggregate on the ultimate strength is also investigated.

3413
Shah, S. P., Li, Z., and Lange, D. A., "PROPERTIES OF AGGREGATE-CEMENT INTERFACE FOR HIGH PERFORMANCE CONCRETE," Proceedings of the 9th Conference on Engineering Mechanics, May 24-27, 1992, College Station, TX; Ed. by Loren D. Lutes and John M. Niedzwecki; ASCE, New York, 1992, pp 852-855.

An experimental study of the interfacial zone between aggregate and cement paste was undertaken. Various factors such as type of aggregate, treatment of aggregate surface, mixing process and incorporation of silica fume were investigated. A newly developed push-out method continuously measured force and slip displacement of the interface during loading. The interfacial properties of the transition zone were characterized using a mathematical model and the microstructure of the interface was examined by electron microscopy. It was found that the microstructure and properties of the interfacial zone can be significantly improved by aggregate pretreatment and mixing methods.

3414
Shindoh, T., Matsuoka, Y., Tangtermsirikul, S., and Sakamoto, J., "EFFECT OF VARIATION OF MATERIAL QUALITY ON PROPERTIES OF SUPER WORKABLE CONCRETE," Transactions of the Japan Concrete Institute, 1992, Vol. 14, pp 71-78.

High flowability and high resistance to segregation are significant characteristics required for super workable concrete. However, since these are two essentially opposite performance characteristics, they have a tendency to be sensitive to fluctuation of material as compared with conventional concrete when the super workable concrete is manufactured in a concrete plant. In this study the authors investigated the influence of fluctuation of material quality, such as surface moisture and grading of the fine aggregate, on the filling ability of the super workable concrete.

3415
Sicard, V., Francois, R., Ringot, E., and Pons, G., "INFLUENCE OF CREEP AND SHRINKAGE ON CRACKING IN HIGH STRENGTH CONCRETE," Cement and Concrete Research, Jan 1992, Vol. 22, No. 1, pp 159-168.

Efficient use of high strength concrete (HSC) depends on a thorough understanding of its long term behaviour. However, its good mechanical performance must not blind its durability properties which are affected by cracking, as recent studies have shown. This paper deals with surface microcracking developed both by creep and shrinkage on young age loaded HSC. The HSC cylinders were stored for 400 days in an air conditioned room (50% RH and 20 degree C). Creep load up to 32 MPa was applied 28 hours after batching. Moreover, the effect of the desiccation was studied in unloaded samples. Microcracking was observed by SEM with replica technique and analyzed with the stereological tools of total projections. The main conclusion is that the intensity of the compressive creep load disturbs the orientation and density of surface microcracking due to desiccation and that recovery after unloading induces surface microcracking, which is strongly oriented in a given direction.

3416
Simon, M. J., Jenkins, R. B., and Hover, K. C., "THE INFLUENCE OF IMMERSION VIBRATION ON THE VOID SYSTEM OF AIR ENTRAINED CONCRETE." in Durability of Concrete: The G. M. Idorn International Symposium held at the 1990 Annual ACI Convention in Toronto, Ontario, Canada; Ed. by Jens Holm and Mette Geiker; American Concrete Institute, Detroit, MI, 1992, pp 99-126. (ACI SP-131)

Experiments were conducted to determine the influence of immersion vibration on the air-void system parameters of air-entrained concrete, as a function of both radial distance and depth from the point of vibrator insertion. For a 1-1/2 inch (40 mm) diameter immersion vibrator, one could conclude that vibration has little or no effect on air-void systems at a distance of 5, 8 or 10 inches (125, 200, 250 mm) from the point of insertion. The same vibrator in the same concrete can reduce the total air content by 50 percent, and increase specific surface by as much as 100 percent directly at the point of vibrator insertion. Which effect might occur in hardened concrete depends on the selection of core location relative to point of vibrator insertion. These observations have implications for specifying, casting, and testing air-entrained concrete.

3417
Snyder, M. B. and Janssen, D. J. "FREEZE-THAW RESISTANCE IN CONCRETE - AN ANNOTATED BIBLIOGRAPHY," Final Report, Michigan State University, East Lansing, MI, 1992, vii, 226 pp. (SHRP-C/UFR-92-617; PB94-102589)

Over 550 citations relevant to the phenomenon of freezing and thawing of concrete are presented, and detailed abstracts of studies on the mechanism of frost action as well as case histories and laboratory investigations are provided. Peripheral topics such as autogenous healing, which helps explain the delay in appearance of D-cracking are included. Studies related to ceramics, geology, physics and soil physics are included for the insight they provide into the roles of moisture movement and ice crystal growth in frost heave and cracking of porous solids. Author and subject indexes are included.

3418
"STATE-OF-THE-ART REPORT ON HIGH STRENGTH CONCRETE," Structural Engineers Trading Organisation, London, 1992, 55 pp.

Currently available information about high-strength concrete is summarized. Topics discussed include selection of materials, concrete mix proportioning, batching, mixing, transporting, placing, control procedures, concrete properties, structural design, economics, and applications. A bibliography is included.

3419
"STRUCTURAL EFFECTS OF ALKALI-SILICA REACTION: TECHNICAL GUIDANCE ON THE APPRAISAL OF EXISTING STRUCTURES," Structural Engineers Trading Organisation, London, 1992, 45 pp.

This report describes the development of damage caused by the alkali silica reaction (ASR) to structures in the United Kingdom. These include bridges. It then presents the chemical processes of ASR, and discusses the physical effects of such processes on concrete. The overall behaviour of structures with ASR is also considered. The procedure for appraising an individual structure is then presented. This includes sections on: a) diagnosis and assessment of reaction severity; b) appraisal of structure strength; and c) appraisal of structural serviceability. The management of ASR affected structures is then presented. This includes methods for inspections, instrumentation, and monitoring.

3420
"STRUCTURAL LIGHTWEIGHT AGGREGATE CONCRETE PERFORMANCE," Papers presented at the American Concrete Institute 1991 Fall Convention, Dallas, TX; Ed. by Thomas A. Holm and Alexander M. Vaysburd; American Concrete Institute, Detroit, MI, 1992, vi, 424 pp. (ACI SP-136)

This volume contains papers presented at the November 14, 1991, technical session of the American Concrete Institute fall convention in Dallas, Texas. Planning for this symposium was in response to the interest of the construction industry and engineering community in using structural lightweight concrete in severe environment applications. The speakers addressed topics ranging from fundamental laboratory studies to case histories of concrete performance. The papers are as follows: High Strength Lightweight Aggregate Concrete for Arctic Applications--Part 1, Part 2, and Part 3, G. C. Hoff; The Advantages of Using Lightweight Concrete in a Medium Rise Building and Adjoining Post-Tensioned Parking Garage, R. Trumble and L. Santigo; Lightweight Concrete Bridges for California Highway System, J. E. Roberts; Lightweight Microsilica (Silica Fume) Concrete in the USA, M. D. Luther; Durability of Lightweight Concrete and Its Connections with the Composition of Concrete, Design and Construction Methods, A. M. Vaysburd; High Ductility, High Strength Lightweight Aggregate Concrete, D. E. Berner; Influence of Compressive Stress on the Permeability of Concrete, T. W. Bremner, T. A. Holm, and J. M. McInerney; Flexural Behavior Including Ductility of High Strength Lightweight Concrete Members under Reversed Cyclic Loading, S. K. Ghose, D. P. Narielwala, S. W. Shin, and J. Moreno; Pore Structure and Carbonation of Lightweight Concrete after 10 Years Exposure, R. N. Swamy and E. D. Jiang; and Fatigue Strength and Endurance Limit of Lightweight Concrete, V. Ramakrishnan, T. W. Bremner, and V. M. Malhotra.

3421
Tabatabai, H. and Dickson, T. J., "COMPREHENSIVE STRENGTH AND DURABILITY EVALUATION OF 34-YEAR OLD POST-TENSIONED CONCRETE BRIDGE GIRDER," Final Report, Construction Technology Laboratories, Skokie, IL, 1992, 98 pp.

The major objective of the research effort reported here was to evaluate the condition of a 34-year old post-tensioned bridge girder through laboratory testing. This evaluation included structural strength and serviceability, state of corrosion of prestressing elements (wires, ducts, and anchorates), material properties, and correlation of the condition of concrete and grout at various locations with the observed corrosion. In addition, the overall condition of the bridge from the corrosion standpoint was to be evaluated through a field condition survey of the bridge including non-destructive tests. The field surveys were sponsored by a separate FHWA project.

3421a
Teng, Z. and Ye, Z., "BOND BEHAVIOR OF DEFORMED BARS IN HIGH STRENGTH CONCRETE," in Bond in Concrete: From Research to Practice, Proceedngs of the CEB International Conference held at Riga Technical University, Oct. 15-17, 1992, Riga, Latvia, Vol. 2, Topics 3-7, pp. 4-11 to 4-18.

To determine the bond-slip behavior of deformed bars in high strength concrete, 62 pull-out specimens were tested. The two types of bond failure were studied: splitting failure and shearing failure. In the tests, the cube compressive strength of concrete varied from 60 N/mm2 to 100 N/mm2. The other parameters were varied: bar diameter, concrete cover, embedment length and confining reinforcement. Results of tests using high strength concrete are compared with similar tests on specimens constructed of normal strength concrete.

3422
Thomas, M. D. A. and Mathews, J. D., "CARBONATION OF FLY ASH CONCRETE," Magazine of Concrete Research, Sep 1992, Vol. 44, No. 160, pp 217-228.

The carbonation of fly ash concrete is reported, with particular emphasis on the role of curing. Concretes with nominal strength grades C25, C35 and C45 and a range of fly ash levels (0-50%) were exposed to various treatments during the first 28 days; i.e. different moist curing periods and a range of ambient temperatures and relative humidities after curing. After 28 days the concretes were stored either internally or externally (sheltered) and the rate of carbonation was monitored. The results emphasize the importance of adequate curing for concrete durability, irrespective of the presence of fly ash. In some cases increasing the initial curing period from 1 to 7 days had the effect of reducing carbonation by 50%. Concretes with up to 30% fly ash carbonated to a similar or slightly greater degree compared with OPC concretes of the same strength grade. However, concretes containing 50% fly ash carbonated at significantly greater rates. A graphical model is presented which allows prediction of the carbonation rate to be made from a knowledge of the concrete mix (strength grade and fly ash content), degree of curing, ambient conditions during and after casting, and type of exposure.

3423
Tia, M., Bloomquist, D., Yang, M. C. K., Meletiou, C. A., Amornsrivilai, P., Shih, C., Richardson, D., and Bobson, E., "EXTENSION STUDY OF MODULUS OF RUPTURE AND PERMEABILITY OF STRUCTURAL CONCRETE IN FLORIDA FOR DEVELOPMENT OF A CONCRETE PERFORMANCE SPECIFICATION," Final Report, Department of Civil Engineering, University of Florida, Gainesville, FL, 1992, Vol. 1, 388 pp.

A field permeability test (FPT) method which was developed in a preceding study was implemented in the testing and evaluation of thirteen selected marine concrete structures in Florida. Core samples of the site concrete tested by the FPTs were extracted and evaluated in the laboratory by means of the standard rapid chloride permeability test. The results of the rapid chloride permeability test were found to be linearly related to the water permeabilities as measured by the FPT. The FPT method was found to be able to provide a relative measurement of permeability which can be used as an indicator of the quality and performance characteristics of structural concrete. A framework of procedure for assessment of durability of existing concrete structures using the FPT method was proposed. An extensive laboratory testing program was conducted to investigate the mechanical properties and the permeability of structural concretes made with Florida aggregates and out-of-state aggregates. The scope of the study covered three water-cement ratios (0.45, 0.38 and 0.33), two pozzolans (Class F fly ash and silica fume), nine aggregate types and three moist-curing durations. Type II cement was used. The tests performed on the hardened concrete included compressive strength, splitting tensile strength, modulus of rupture, modulus of elasticity, water permeability, rapid chloride permeability, and water absorption tests. For the ranges of w/c ratios used in the study, the strength of aggregate has little effect on the strength of concrete. Florida limestone can produce moderately high strength concrete (10,000 psi) as the dense limestone from out of state. Empirical relationships between different concrete properties were developed for Florida concretes. Relationships among water permeability, rapid chloride permeability and water sorptivity test results were also established.

3424
Tia, M., Bloomquist, D., Yang, M. C. K., Meletiou, C. A., Amornsrivilai, P., Shih, C., Richardson, D., and Bobson, E., "EXTENSION STUDY OF MODULUS OF RUPTURE AND PERMEABILITY OF STRUCTURAL CONCRETE IN FLORIDA FOR DEVELOPMENT OF A CONCRETE PERFORMANCE SPECIFICATION, APPENDICES," Final Report, Department of Civil Engineering, University of Florida, Gainesville, FL, 1992, Vol. 2, 203 pp.

This volume contains the appendices to accompany the final report. The appendices are as follows: (A) Application of the Proposed Testing Program for Marine Structures - A Worked Example; (B) Analysis of Results of Compressive Strength Tests; (C) Properties of Trial Batches and Amount of Admixture Used in Trial Batches; (D) Mix Proportions and Properties of Fresh Concretes; (E) Summary of Test Results; and (F) Summary of Burr-Foster Q-Test Results.

3425
Whiting, D. and Dziedzic, W., "EFFECTS OF CONVENTIONAL AND HIGH-RANGE WATER REDUCERS ON CONCRETE PROPERTIES," Portland Cement Association, Skokie, IL, 1992, Research and Development Bulletin No. RD107.01T, 24 pp.

Fresh concretes were prepared using cements of high and moderate C3A contents and having a cement content of 323 kg/cu m (545 lb/cu yd) and a water-to-cement ratio of 0.50. Conventional water-reducing agents based on lignosulfonates and carboxylic acids were used to reduce water and cement contents by 8 to 9%. Second generation high-range water-reducing admixtures (HRWR) were used to reduce cement and water contents by 15 to 16%. Testing included slump loss, air loss with time, setting time, and bleeding. Similar tests were carried out on flowing concretes, where cement and water contents were maintained constant and HRWR was added to increase initial slump levels to 175 to 225 mm (7 to 9 in.). In this series, testing was carried out at both 23 deg C (73 deg F) and 32 deg C (90 deg F). Hardened concrete specimens were prepared and tested for freeze-thaw resistance, resistance to deicer scaling, permeability to chloride ion, drying shrinkage and compressive strength development. In addition, the air-void systems of concretes containing second-generation HRWR and air-entraining admixtures were analyzed by linear traverse. Use of chemical admixtures to reduce both water and cement contents resulted in accelerated rates of slump loss and shorter working times compared to controls. When used to produce flowing concretes, working times were equivalent to those for mixes not containing the admixtures. In general, setting times were increased from 1 to 2 hr at 23 deg C (73 deg F) and by lesser amounts at 32 deg C (90 deg F). Bleeding of flowing concretes was greater than that of control mixtures, especially when a copolymer-type HRWR was used. Rate of air loss was significantly greater in cement-reduced mixtures containing HRWR compared with controls; however, air loss rates in flowing concretes were roughly equivalent for all mixtures tested. Additionally, drying shrinkage may be moderately increased in these concretes.

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